Bistable magnetic latching relay

ABSTRACT

A magnetic-latching relay in which an armature is movable between a closed position engaging one end face of a core and an open position spaced from this end face and in which two windings are provided about the core, one of which provides, when energized, a magnetic field moving the armature to closed position and the other, when energized, moving the armature to open position. The relay includes further an annular permanent magnet, surrounding the end portion of the core on which the end face cooperating with the armature is provided, to keep the armature, when brought to the closed position by energizing the one winding, in said closed position even after the one winding is deenergized.

U United States Patent [1113,569,890

[72] Inventor Ezio gui 3,076,880 2/ 1963 Ehrismann 335/128 via Cavour14,Buguggiate, vargse, 3,1 53, 1 Martin. [21] Appl. No. 787,004 FOREIGNPATENTS [22] Filed Dec. 26, 1968 983,303 2/1965 Great Britain 335/230[45] Patented Mar. 9, 1971 v [32] Priority Dec. 29 1967 PnmaryExarnmeF-Harold Broome 33] 81y Attorney-Michael S. Striker [31]24517A/67 [54] BLSTABLE MAGNETIC LATCHING RELAY ABSTRACT: Amagnetic-latching relay in which an armature 5 Claims 1 Drawin 1smovable between a closed position engaging one end face of a core and anopen position spaced from this end face and in US. Cl two winding areprovided about the core one of 335/234 provides, when energized, amagnetic field moving the arma- [51] Int. Cl HOlh 9/24 tul-e to l dition and the other, when energized, moving ofsearch the annature toopen position The relay includes further an 229, 253,254, 128 (Gummy)annular permanent magnet, surrounding the end portion of the core onwhich the end face cooperating with the armature [56] References Citedis provided, to keep the armature, when brought to the closed UNITEDSTATES PATENTS position by energizing the one winding, in said closedposition 2,81 1,601 10/1957 Somers 335/170 even after the one winding isdeenergized.

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, Patented -March 9, 1971 3,569,890

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Ell-STABLE MAGNETIC LATCHING RELAY This invention relates to a bistablemagnetic latching relay of a type employing a mobile armature kept instable attracted position also after the power of the excitation coilhas been removed, by means of a proper magnetic-latching field and isreleased only by the excitation of an auxiliary coil generating amagnetic field reverse to the latching field.

Known relays of this kind belong to two separate types:

the first type employs a magnetic core saturated by the excitation of atripping coil, apt to keep a residual magnetism which is great enough tohold the armature in stable latching position against the reset springs,also after the excitation of the coil has been finished.

The release of the armature is achieved by generating (by means of anauxiliary coil) a magnetic field which is reversed to the residual one.

The second type employs a permanent magnet placed near the end of thecore which has the greatest distance from the useful gap with regard tothe armature. This permanent magforming the useful gap and which isdesigned to rest on the core, and a secondary surface which is attractedby the permanent magnet in the open armature position.

Due to those components the main circuit generated by the permanentmagnet is realized when the armature is attracted for the excitation ofthe main coil and remains attracted also when this excitation stops.

The main circuit involves the permanent magnet, the core and thearmature.

When the armature is released for the excitation of the secondary coil,the secondary useful surface of this armature comes to rest on thepermanent magnet establishing a derived circuit which involves only thepermanent magnet and the secondary surface of the armature. As aconsequence the armature is kept in the two stable positions, i.e.;closed" and open" due to the influence of the permanent magnet.

For the first type of relay it is necessary to use high qualitymaterials in order to obtain a sufficient residual magnetic field and tomanufacture the relay with utmost precision to reduce to a minimum thegaps which requires employing high skilled workers and expensiveequipment.

For the second type beside the use of high quality materials andprecision manufacture it is necessary to have a rather strong permanentmagnet and a convenient operation is obtained only owing to a particularshape which has to be given to the armature and to the magnetic circuit.In fact, if there were no secondary useful surface of the armature,which acts in the phase of the open relay, the armature would always beattracted in the closed position, overwhelming the antagonistic force ofthe reset springs.

This invention relates to a bistable latching relay employing apermanent magnet placed on the end of the core next to the latchingsurface of the armature while the latter has a simple shape.

The permanent magnet has a latching force which allows not to attractthe armature when it is open, but to keep it stably closed when thearmature has been brought in closed position through the excitation ofthe main tripping coil, while a secondary coil generates a magneticfield reverse to the field of the core in order to allow that the resetsprings reset the armature in the open position.

According to a preferred constructive form, the end of theelectromagnets core upon which the armature drops, projects by apredetermined length beyond the coil. The permanent magnet is placed onthis end and takes a ring shape with a prefixed polarity. The end of thecore projects beyond this electromagnet for a length sufficient to allowthe armature to rest on it.

Between the permanent magnet and the core is left a sufficientring-shaped gap to avoid that the lines of force of the permanentmagnetic field close directly on the core, but are compelled to pass forthe greatest part through the mobile armature when in closed position. v

The first advantage offered by this invention is that the presence ofthe permanent magnet in the proximity of the armature does not require aperfect fitting between the surface in contact with the armature and theend of the core and therefore eliminates the necessity of precisionmanufacture.

An additional advantage is that the presence of a little residualmagnetism of the core does not impair operation of the relay, on thecontrary it is possible to exploit ad-' vantageously the sum hole themagnetic field of this residual magnetism and of the magnetic field ofthe permanent magnet to keep the armature latched; this allows to use aweak per manent magnet and to use for the core a less expensive material thus realizing a magnetic-latching relay at low cost and easy toproduce while maintaining unaltered the requirements of a safe andstable latching of the armature.

The invention is illustrated as a not limiting example of a constructiveform in the FIGURE of the drawing showing in enlarged scale alongitudinal cross section of the relay.

With reference to this FlQURE the relay which is object of theinvention, consists of a double winding comprising a main coil ofexcitation 1 and an auxiliary coil 2 for the demagnetization. Thesewindings are wound on a sleeve 3 limited at the two ends by twoflangest4 and 5 and sleeve 3 houses in its cylindrical portion themagnetic core 6 which is of a material apt to keep a little residualmagnetism. This core is fixed to the bent surface 7 of a yoke orL-shaped member with a fixing screw 9 passing through the mentioned part7 and threading into a blind, threaded hole of the core. Between thesupport 7 and the adjacent core is placed a washer 10 serving to keepthe core 6 in a fixed axial position with regard to the sleeve 3.

The core 6 is longer than the sleeve and its free end 6' projects beyondthe side 5 by a predetermined length, as explained below. 7

A permanent ring-shaped magnet" ll having an internal diameter which islarger than the diameter of the core 6, is placed about the end 6' sothat there is left a ring-shaped gap which may be filled with anonmagnetic material, for instance a ring 12 of plastic material. Thepermanent magnet preferably is made of plastic bonded ferrite, so thatbesides having good magnetic properties it may be produced at low cost.

The core 6 projects beyond said permanent magnet 11 for a small step 13,so that its plane end face provides a suitable support for the mobilearmature l4.

The mobile armature 14 has the shape of a bent arm and its elbow 15 isfulcrummed on the bottom of a clevis 16 obtained from the yoke 8. Ablade spring 17 exercises a pressure on the armature compelling thelatter against its fulcrum.

A branch 14' of the armature 14 support a pressure member 18 allowing tomove the elasticrblades 19 carrying the mobile contacts towards thefixed blades 20 carrying the fixed contacts and aligned by rigidsupports 21. The elastic blades 19 form also the reset spring of themobile armature l4.

In a preferred constructive form there is also a base 22 of insulatingmaterial shaped to show a seat 23 for the engagement of the yoke 8, andthe seats 24 and 25 in which are fixed the supports 26 and 21 of thecontacts 19 and 20. The fixing is done by means of the screws 27 and 28which reach to outside grooves respectively 29 and 30 of the base tosupport the terminals 31 and 32 to which arrive the electrical contactsconnected to the contacts and which are clamped by the screws 33 and 34respectively.

The alignment with the core 6 and the base 22 shows a groove 35 in whichenters the spring 17, while its end is engaged between the raised wall36 and the opposite side 37 formed by the same groove 35. The terminals38 equipped with fixing screws 39 serve for the connection of the lineconductors of the winding by means of the screws 40 and conductingplates 41.

A housing 42 serves to cover the base and all the components standing onthe latter, however, without supporting the components themselves.

The relay operates as follows:

When the coil 1 is excited, the core 6 attracts the armature 14 whichcomes to rest on the plane end 6" of the core. When the power is removedfrom said coil 1 the armature stays attracted by the permanent magnet 11while its lines of force pass mostly through the armature itself. Incase a residual magnetism remains in the core 6, which alone is notsufficient to hold the armature against the reset force of the elasticblades 19, this magnetism is added to that of the permanent magnetthereby contributing to a rise the attraction force on said armature.The gap 12 between the magnet 11 and the core 6 serves to avoid that thelines of force of this permanent magnet close directly on the core, butare compelled to pass through the armature 14.

Thus it is possible to obtain a latching position of the armature whichis so stable that it is maintained also in case of transmission ofshocks an vibrations to the relay.

In order to achieve the opening of the armature 14 it is necessary tosupply the coil 2, which has to create a magnetic field reverse to thefield established by a possible residual magnetism of the core and bythe permanent magnet 11 and which is sufficient to reset in the openposition the armature by means of the antagonism of the elastic blades19.

Of course the invention can be realized according to other constructiveforms different from the one described above without trespassing thelimits of the patent.

lclaim:

l. A magneticlatching relay which is maintained stable in closed as wellas in open position and comprising a core having an end face and beingformed from magnetizable material; an armature located adjacent said endface movable between an open position spaced from said one end face anda closed position engaging the same; a main winding about said core forgenerating, when energized, a magnetic field which moves said armatureto said closed position; an auxiliary winding about said core forgenerating, when energized, a magnetic field opposite to the fieldgenerated by said main winding, said core having at said one end face anend portion projecting beyond said windings; and a ring-shaped permanentmagnet surrounding said end face of said core radially spaced therefromto define an annular gap between said core and said permanent magnet,said permanent magnet producing a magnetic field in the same directionas the main winding so that said armature, after being moved byenergizing said main winding to said closed position, will be directlyattracted by said permanent magnet and stay in said close position aftersaid main winding is deenergized until said auxiliary winding isenergized.

2. A relay as defined in claim 1, and including a ring of nonmagneticmaterial substantially filling said annular gap.

3. A relay as defined in claim 1, and including biassing means forbiassing said armature to said open position, and wherein said core isformed of a material apt to keep a notable residual magnetism which,however, alone is not sufficient to keep said armature in said closedposition against the force of said biasing means, but will do so incombination with the force of said permanent magnet.

4. A relay as defined in claim 3, and including an L-shaped member ofmagnetizable material having a short arm in magnetic contact with theother end face of said core, said armature being in the form of atwo-arm lever having one arm facing said one end face and beingpivotally mounted intermediate its ends on the end of the other arm ofsaid L-shaped member, said biasing means comprising a leaf-springcarrying a movable contact of said relay, said leaf-spring cooperatingwith the other arm of said two-arm lever.

5. A relay as defined in claim 1, wherein said permanent magnet is madefrom plastic bonded ferrites.

1. A magnetic-latching relay which is maintained stable in closed aswell as in open position and comprising a core having an end face andbeing formed from magnetizable material; an armature located adjacentsaid end face movable between an open position spaced from said one endface and a closed position engaging the same; a main winding about saidcore for generating, when energized, a magnetic field which moves saidarmature to said closed position; an auxiliary winding about said corefor generating, when energized, a magnetic field opposite to the fieldgenerated by said main winding, said core having at said one end face anend portion projecting beyond said windings; and a ring-shaped permanentmagnet surrounding said end face of said core radially spaced therefromto define an annular gap between said core and said permanent magnet,said permanent magnet producing a magnetic field in the same directionas the main winding so that said armature, after being moved byenergizing said main winding to said closed position, will be direcTlyattracted by said permanent magnet and stay in said close position aftersaid main winding is deenergized until said auxiliary winding isenergized.
 2. A relay as defined in claim 1, and including a ring ofnonmagnetic material substantially filling said annular gap.
 3. A relayas defined in claim 1, and including biassing means for biassing saidarmature to said open position, and wherein said core is formed of amaterial apt to keep a notable residual magnetism which, however, aloneis not sufficient to keep said armature in said closed position againstthe force of said biasing means, but will do so in combination with theforce of said permanent magnet.
 4. A relay as defined in claim 3, andincluding an L-shaped member of magnetizable material having a short armin magnetic contact with the other end face of said core, said armaturebeing in the form of a two-arm lever having one arm facing said one endface and being pivotally mounted intermediate its ends on the end of theother arm of said L-shaped member, said biasing means comprising aleaf-spring carrying a movable contact of said relay, said leaf-springcooperating with the other arm of said two-arm lever.
 5. A relay asdefined in claim 1, wherein said permanent magnet is made from plasticbonded ferrites.